Had the same thing happen with a bakery owner who wanted a menu design for $100. I did it, she loved it, then she turned around and told me I was nuts for charging so little. Raised my base to $500 the next month and the first three people who heard the number just nodded and pulled out their checkbooks. The cheap price was actually scaring off the good clients because they figured something must be wrong with the work. You did the right thing and that contract detail about two rounds of edits is smart, saves you from the endless back and forth. Keep going up until somebody actually flinches.

Wait, people are still using PVA on old paper in the first place? I thought that stuff was mostly for bookbinding repairs where you actually want a hard, stiff bond, not for fragile pages that need to move with changes in humidity. Wheat paste makes sense for pre-1900 paper because it stays flexible and can be reversed later with water if someone needs to undo the repair, while PVA just locks everything down forever and cracks when the paper flexes. I made the switch years ago and never looked back, though I will admit the paste takes some getting used to since it sets slower and you have to cook it yourself. The trick is getting the consistency right, too thick and it dries shiny, too thin and it soaks the paper and stains it. Just do not expect it to hold like glue on a modern paperback, because that is a totally different job.